This invention pertains generally to scroll apparatus and more specifically to scroll compressors of the co-rotating type wherein both scroll members rotate on parallel, offset axes. With still more particularly, this invention relates to high-side co-rotating refrigerant scroll compressors wherein compressed refrigerant gas and the oil entrained therein is discharged through the drive shaft of the drive scroll member and wherein the distal end of the scroll member drive shaft is rotatably supported in a bearing proximate the location at which discharge gas and entrained oil exits the drive shaft.
Scroll compression apparatus is typically comprised of two scroll members each of which has an involute wrap. The wraps of the scroll members extend from an end plate and are in an interleaved relationship. Relative orbital motion of one scroll member with respect to the other causes the creation of a series of pockets between the scroll wraps which, in operation, decrease in volume thereby compressing any gas trapped therein.
Scroll compressors are typically of the type in which one of the scroll members is fixed while the other orbits thereabout or the co-rotating type in which both scroll members rotate on parallel but offset axes. In a co-rotating scroll compressor one of the scroll members is characterized as the drive scroll and the other as the idler scroll.
The drive scroll member is driven through a drive shaft which is integral to and extends from the end plate of the drive scroll member or by the mechanical linkage of a drive shaft to the drive scroll member. The scroll member drive shaft, whether integral to the drive scroll member or mechanically linked thereto, penetrates and is fixedly coupled for rotation with the rotor of the electric motor which drives the compressor.
Hermetic compressors (compressors in which both the drive motor and compression mechanism are disposed in a hermetic shell), including those of the scroll type, are categorized as being of the high side or low side type. A high side compressor is one in which the drive motor is disposed in a portion of the compressor shell which is at compressor discharge pressure when the compressor is in operation while a low side compressor is one in which the drive motor is disposed in the portion of the compressor shell which is at suction pressure in operation.
It has been prospectively determined, with respect to hermetic co-rotating scroll compressors, to be advantageous to employ a high side design in which the compressor drive motor is disposed physically above the compression mechanism and to use the drive shaft of the drive scroll member to communicate compressed refrigerant gas out of the compression mechanism. Exemplary in that regard are U.S. Pat. Nos. 4,927,339 and 5,080,566, the former being assigned to the assignee of the present invention and incorporated herein by reference.
It has been found by the inventors of the present invention that due to the tipping moments to which the scroll members of a co-rotating scroll compressor are exposed in operation, the use of two bearings to rotatably support the drive scroll member drive shaft, rather than the single bearing arrangements taught by the patents mentioned above, is advantageous. The unique nature and effect of the tipping forces to which co-rotating scroll members are exposed and various methods and apparatus by which the effects of such tipping can be accommodated and/or reduced are discussed in U.S. Pat. Nos. 5,099,658; 5,129,798 and 5,142,885, all assigned to the assignee of the present invention and all of which are incorporated herein by reference.
With respect to the use of a bearing at the upper end of the drive shaft of the drive scroll member in a high side co-rotating scroll compressor, where the compressor motor is disposed vertically above the compressor mechanism and where the drive shaft is used to convey compressed refrigerant gas therefrom, certain difficulties are presented in the lubrication of that bearing. In particular, the need exists to communicate lubricant quickly to that bearing at compressor startup and to provide lubricant to that bearing continuously during compressor operation. Although no such bearing arrangement in a co-rotating scroll compressor is known (no co-rotating scroll compressor is known to be in commercial production anywhere in the world as of the filing date hereof), much less one in which the drive scroll member is used to conduct compressed gas from the compression mechanism, similar arrangements in compressors other than of the scroll type are known such as the one described in U.S. Pat. No. 5,087,170 to Kousokabe.
The Kousokabe patent teaches a non-scroll compressor having a solid drive shaft and an arrangement in which discharge gas is routed upward through the rotor-stator gap of the motor into the vicinity of an upper bearing. Lubricant disentrained from such gas drains to the vicinity of the upper bearing to assist a primary source of lubricant in the lubrication of that bearing.
The upper bearing in Kousokabe is primarily lubricated by a pump which delivers oil upwardly to the bearing from an oil sump disposed below the drive motor when the compressor is driven at sufficiently high speeds. At lower speeds, when the pumping action is insufficient to provide for the full lubrication needs of that bearing using oil from the sump, the disentrained oil draining to the vicinity of the upper bearing is used to assist in its lubrication.
A similar oil separation/lubrication arrangement is suggested in an earlier U.S. Pat. No. 4,995,789, to Fujio. Like the Kousokabe arrangement, a solid drive shaft is rotatably supported in an upper bearing in a hermetic compressor. Compressor discharge gas is delivered through a conduit which is routed external of the compressor shell to the vicinity of the upper bearing. Entrained lubricant is there separated and drained to the vicinity of the upper bearing for lubrication thereof.
Unlike like the Kousokabe arrangement, the Fujio compressor is a scroll compressor but one in which one of the scroll members is fixed and which employs only two bearings. Further, the scroll member drive shaft in Fujio, which is solid as mentioned above, drives the orbiting scroll member through a linkage. Additionally, compressor discharge gas is routed downwardly through the fixed scroll member, then outside of the compressor shell prior to final discharge therefrom.
There continues to be a need for a viable arrangement, in a high side co-rotating scroll compressor in which compressed gas is discharged through the drive scroll member drive shaft, by which to lubricate the bearing which rotatably supports the distal end of the drive shaft.